1. Technical Field
The present disclosure relates to sulfur composite lithium ion batteries.
2. Description of Related Art
Sulfur has great potential for high-performance lithium ion batteries due to their large specific capacity, abundant resources and low cost.
Elemental sulfur particles dispersed in a conductive agent are used as a cathode active material of the lithium ion battery. The elemental sulfur particle has a large diameter of micrometer-scale. The external surface of the elemental sulfur particle firstly reacts with an electrolyte of the lithium ion battery during a discharge process of the lithium ion battery. The sulfur would be reduced to form Li2S and Li2S2 having a poor conductivity. The Li2S and Li2S2 would gradually cover the surface of the elemental sulfur particle in a form of solid state film. The internal sulfur cannot react with the electrolyte due to an obstruction of the Li2S and Li2S2. Thus, an active area of the elemental sulfur particle is decreased.
A liquid electrolyte capable of dissolving the Li2S and Li2S2 is adopted to promote the reaction between the electrolyte and the elemental sulfur particles. However, an intermediate product capable of dissolving in the electrolyte can be formed during the reaction. The intermediate product is polysulfide. Thus, an irreversible loss of sulfur is induced, thereby decreasing a capacity of the lithium ion battery.
What is needed, therefore, is to provide a sulfur composite lithium ion battery having a large utilization of the sulfur.